Substrate heating method

ABSTRACT

A substrate heating device includes: heating modules each having a processing vessel within which a heating plate is disposed, an gas inlet port for introducing a purge gas into a processing atmosphere, and an exhaust port for exhausting the processing atmosphere; individual exhaust paths each connected to the exhaust port of the heating modules; a common exhaust path connected to downstream ends of the individual exhaust paths of the heating modules; a branch path branched from the individual exhaust paths and opened to the outside of the processing vessel; and an exhaust flow rate adjusting unit configured to adjust a flow rate ratio of an exhaust flow rate of a gas exhausted from the exhaust port into the common exhaust path and an introduction flow rate of a gas introduced from the outside of the processing vessel into the common exhaust path through the branch path.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Divisional Application of U.S. patent application Ser. No.14/816,550, filed Aug. 3, 2015, an application claiming the benefit ofJapanese Patent Application No. 2014-162764, filed on Aug. 8, 2014, inthe Japan Patent Office, the disclosure of which is incorporated hereinin its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to a substrate heating device and asubstrate heating method which heat a substrate mounted on a heatingplate, and a computer-readable storage medium including a computerprogram.

BACKGROUND

In a semiconductor device manufacturing process, a process of heating asemiconductor wafer (hereinafter referred to as a “wafer”) as asubstrate having a chemical solution coated on the surface thereof by aheating device is included. In order to remove a sublimate generatedfrom the chemical solution, the heating process is often performed bymounting the wafer on a heating plate installed within a processingvessel and exhausting the interior of the processing vessel. Forexample, a semiconductor manufacturing apparatus having a hierarchicalstructure is sometimes configured such that heating devices areinstalled at individual levels and heating modules each including theprocessing vessel are installed in the respective levels. For example,the respective processing vessels installed at the same level areconnected to a common exhaust duct through an exhaust pipe provided witha damper. The interior of the exhaust duct is exhausted at apredetermined exhaust flow rate.

In the heating modules, with a view toward the compatibility ofincreasing film thickness uniformity within a plane of the wafer andreliability of removing a sublimate from the interior of the processingvessel, consideration has been given to changing an exhaust flow rate inthe processing vessel while processing one wafer. However, in theaforementioned heating devices, if the exhaust flow rate in oneprocessing vessel is changed, the exhaust flow rate in anotherprocessing vessel sharing the exhaust duct with the one processingvessel is also changed. For that reason, it becomes possible that theability to remove the sublimate from the interior of another processingvessel is reduced and the film thickness uniformity deteriorates.

With regard to the change of the exhaust flow rate in the processingvessel, a description will be made on one example in which threeprocessing vessels are connected to an exhaust duct. It is assumed thatthe interior of the exhaust duct is exhausted at 30 L/min and furtherthat the respective processing vessels are exhausted at, e.g., 10 L/min,with dampers of exhaust pipes connected to the respective processingvessels kept in an open state. In this state, if the damper of theexhaust pipe connected to one processing vessel is closed and if theexhaust flow rate in one processing vessel becomes equal to 0 L/min, theexhaust flow rate in the remaining two processing vessels is increasedto 30/2=15 L/min. This is because the interior of the exhaust duct isexhausted at 30 L/min.

For example, a heating device which, while processing a wafer, changes asupply amount of a purge gas supplied into a processing vessel is known.There is also known a liquid processing device in which a plurality ofcups is connected to a common exhaust duct through exhaust pipes havingdampers and in which the exhaust flow rates in the respective cups arecontrolled independently of one another. However, these devices are notcapable of solving the aforementioned problem.

SUMMARY

Some embodiments of the present disclosure provide a substrate heatingdevice which includes a plurality of heating modules each having aprocessing vessel for processing a substrate and an exhaust path commonto the respective heating modules and which can accurately control theexhaust flow rates in the respective heating modules. Some embodimentsof the present disclosure provide a substrate heating method which canaccurately control the exhaust flow rates in the respective heatingmodules, and a computer-readable storage medium.

According to one embodiment of the present disclosure, there is provideda substrate heating device, including: a plurality of heating modules,each of which includes a processing vessel within which a heating platefor mounting and heating a substrate is disposed, an gas inlet port forintroducing a purge gas into a processing atmosphere existing within theprocessing vessel, and an exhaust port for exhausting the processingatmosphere; individual exhaust paths, each of which is connected to theexhaust port of each of the plurality of heating modules; a commonexhaust path connected to downstream ends of the individual exhaustpaths of the plurality of heating modules; a branch path branched fromeach of the individual exhaust paths and opened to the outside of theprocessing vessel; and an exhaust flow rate adjusting part configured toadjust a flow rate ratio of an exhaust flow rate of a gas exhausted fromthe exhaust port into the common exhaust path and an introduction flowrate of a gas introduced from the outside of the processing vessel intothe common exhaust path through the branch path.

According to another embodiment of the present disclosure, there isprovided a substrate heating method which makes use of a substrateheating device including: a plurality of heating modules, each of whichincludes a processing vessel within which a heating plate for mountingand heating a substrate is disposed, a gas inlet port for introducing apurge gas into a processing atmosphere existing within the processingvessel, and an exhaust port for exhausting the processing atmosphere;individual exhaust paths, each of which is connected to the exhaust portof each of the plurality of heating modules; and a common exhaust pathconnected to downstream ends of the individual exhaust paths of theplurality of heating modules; and a branch path branched from each ofthe individual exhaust paths and opened to the outside of the processingvessel, the method including: mounting the substrate on the heatingplate; adjusting, with an exhaust flow rate adjusting part, a flow rateratio of an exhaust flow rate of a gas exhausted from the exhaust portinto the common exhaust path and an introduction flow rate of a gasintroduced from the outside of the processing vessel into the commonexhaust path through the branch path, thereby maintaining a low exhauststate in which the processing atmosphere is exhausted at a low exhaustflow rate; and subsequently, adjusting the flow rate ratio with theexhaust flow rate adjusting part, thereby maintaining a high exhauststate in which the processing atmosphere is exhausted at a flow ratehigher than the low exhaust flow rate.

According to another embodiment of the present disclosure, there isprovided a non-transitory computer-readable storage medium which storesa computer program used in a substrate heating device for heating asubstrate mounted on a heating plate, wherein the program incorporatessteps for implementing the aforementioned substrate heating method.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentdisclosure, and together with the general description given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present disclosure.

FIG. 1 is an overall configuration view of a heating device according toan embodiment of the present disclosure.

FIG. 2 is a vertical sectional side view of a heating module whichconstitutes the heating device.

FIG. 3 is a schematic diagram showing a state of a damper of the heatingmodule.

FIG. 4 is a schematic diagram showing another state of the damper of theheating module.

FIG. 5 is a graphical representation showing the relationship between adamper switching timing and a wafer temperature in the heating module.

FIG. 6 is a graphical representation showing the relationship betweenthe damper switching timing and the wafer temperature in the heatingdevice.

FIG. 7 is a schematic diagram showing the states of dampers at aspecified time during the processing of the wafer.

FIG. 8 is a graphical representation showing the relationship betweenthe damper switching timing and the wafer temperature in the heatingmodule.

FIG. 9 is a vertical sectional side view showing another configurationexample of the heating module.

FIGS. 10 and 11 are explanatory views showing another configuration ofthe damper.

FIG. 12 is a graphical representation showing the results of evaluationtests.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present disclosure. However,it will be apparent to one of ordinary skill in the art that the presentdisclosure may be practiced without these specific details. In otherinstances, well-known methods, procedures, systems, and components havenot been described in detail so as not to unnecessarily obscure aspectsof the various embodiments.

A heating device 1 of a wafer W according to an embodiment of thepresent disclosure will be described with reference to the schematicconfiguration view shown in FIG. 1. The heating device 1 is configuredto heat a wafer W whose surface is coated with a chemical solution atthe outside of the heating device 1. In this example, the diameter ofthe wafer W is 300 mm. The chemical solution contains a polymer (alow-molecular-weight polymer) having a relatively low molecular weightand a cross-linking agent. When the chemical solution is heated to,e.g., 250 degrees C., the polymer undergoes a cross-linking reaction andforms an organic film called an SOC film, which is mainly composed ofcarbon. The content percentage of carbon in the organic film is, e.g.,90% or higher. After the heating is performed by the heating device 1, asilicon-oxide-containing film called an SOG film and a resist film arelaminated on the organic film in the named order at the outside of theheating device 1. A pattern formed in the resist film is sequentiallytransferred to the films of lower layers by virtue of dry etching. Thatis to say, the organic film is mainly composed of carbon and is used asa pattern mask for etching the films positioned under the organic film.

In the description of the heating device 1, the heating device 1includes a plurality of heating modules 2A to 2C, each of which heatsthe wafer W, an exhaust duct 11 and a controller 12. The exhaust duct 11is installed so as to extend in a horizontal direction and is connectedat the downstream side thereof to an exhaust path of a factory where theheating device 1 is installed. The downstream ends of exhaust pipes 30forming individual exhaust paths which constitute the heating modules 2Ato 2C are connected to different points of the exhaust duct 11 arrangedalong the extension direction of the exhaust duct 11. That is to say,the exhaust duct 11 constitutes a common exhaust path for the heatingmodules 2A to 2C. The interior of the exhaust duct 11 is alwaysexhausted at a predetermined exhaust flow rate and is heated by a heater(not shown) in order to prevent condensation of a sublimate introducedfrom the heating modules 2A to 2C.

The heating modules 2A to 2C are identical in configuration with oneanother and are capable of independently heating the wafer W. Theheating module 2A whose vertical sectional side view is shown in FIG. 2will be described as one representative example of the heating modules2A to 2C. In FIG. 2, reference numeral 21 designates a horizontalcircular heating plate provided with a heater 22. The heating plate 21is configured to heat the wafer W mounted on the surface thereof. InFIG. 2, reference numeral 23 designates a base which surrounds andsupports a bottom surface and a side surface of the heating plate 21.The base 23 is formed into a bottom-closed cylindrical shape. In FIG. 2,reference numeral 24 designates a flange which forms an upper endportion of the base 23. In FIG. 2, reference numeral 25 designates liftpins penetrating through the heating plate 21 and the base 23 in thevertical direction. The lift pins 25 perform delivery of the wafer Wbetween a transfer mechanism not shown and the heating plate 21.

An erected cylindrical shutter 26 is installed on an outer periphery ofthe flange 24. The upper end portion of the shutter 26 extends outwardat the upper side of the base 23 and the heating plate 21, therebyforming a flange 27. The lower end portion of the shutter 26 extendsinward, thereby forming a ring 28. The ring 28 overlaps with the flange24 of the base 23. The ring 28 is formed so as to prevent leakage of agas from between the shutter 26 and the base 23. In FIG. 2, referencenumeral 29 designates an elevator mechanism which moves the shutter 26up and down with respect to the heating plate 21. When the wafer W isprocessed, the shutter 26 is located at a position shown in FIG. 2. Whenthe wafer W is delivered with respect to the heating plate 21, theshutter 26 is moved down from the position shown in FIG. 2 such that theshutter 26 does not hinder the delivery of the water W.

In the upper side of the shutter 26, a circular cover 31 is installed inan opposing relationship with the heating plate 21 so as to cover theshutter 26 and the heating plate 21. A processing vessel 20 forprocessing the wafer W is configured by the cover 31, the base 23 andthe shutter 26. The interior of the processing vessel 20 is configuredto serve as a wafer processing atmosphere. In a ceiling portion of thecover 31, an exhaust port 32 is formed so as to face the central portionof the wafer W mounted on the heating plate 21. The reason for formingthe exhaust port 32 at the upper side of the wafer W in this way is tomake sure that pressure loss is reduced when exhausting the interior ofthe processing vessel 20 and the exhaust can be performed at arelatively large flow rate. Since a relatively large amount of sublimateis generated from the organic film, it is advantageous to employ theconfiguration capable of increasing the exhaust flow rate. The gapexisting between the cover 31 and the flange 27 of the shutter 26constitutes a gas inlet port 33 extending along the circumferentialdirection of the heating plate 21. The gas inlet port 33 is formed overthe entire circumference of the wafer W. The vertical width of the gasinlet port 33 indicated by H1 in FIG. 2 may be, e.g., from 0.5 mm to 1mm. Furthermore, the height ranging from the front surface of theheating plate 21 to the rear surface of the cover 31, which is indicatedby H2 in FIG. 2, may be, e.g., 30 mm.

One end portion of the exhaust pipe 30 is connected to the cover 31 soas to exhaust the interior of the processing vessel 20 through theexhaust port 32. The other end portion of the exhaust pipe 30 isconnected to the exhaust duct 11 as set forth above. Since the interiorof the exhaust duct 11 is exhausted as described above, the processingatmosphere within the processing vessel 20 is exhausted toward theexhaust duct 11. As the interior of the processing vessel 20 isexhausted in this way, a gas, e.g., air, is admitted from the outside ofthe processing vessel 20 into the processing vessel 20 through the gasinlet port 33 at a flow rate corresponding to the exhaust flow rate ofthe gas exhausted from the interior of the processing vessel 20. Then,the air flows from the peripheral edge portion of the wafer W toward thecentral portion thereof along the radial direction of the wafer W,thereby purging the processing atmosphere. Thereafter, the air flowsinto the exhaust port 32 and is exhausted.

The exhaust pipe 30 is branched to form a branch pipe 34 whichconstitutes a branch path. The other end portion of the branch pipe 34is opened toward an air atmosphere at the outside of the processingvessel 20. A damper 35 which can be opened and closed and whichconstitutes an exhaust flow rate adjusting part is installed in thebranch pipe 34 (see FIG. 1). FIG. 3 shows an upper surface of theheating module 2A. The open state of the damper 35 is schematicallyshown in FIG. 3. The flow of a gas in the heating module 2A of thisstate is indicated by arrows. The gas flow will be described in detail.By exhausting the interior of the exhaust duct 11, air is admitted fromthe air atmosphere into the exhaust duct 11 through the branch pipe 34and the exhaust pipe 30. Accordingly, the total sum of the flow rate ofthe air flowing from the branch pipe 34 into the exhaust pipe 30 and theflow rate of the air exhausted from the interior of the processingvessel 20 becomes equal to the flow rate of the air flowing from theexhaust pipe 30 into the exhaust duct 11. Thus, for example, if the airis admitted from the exhaust pipe 30 into the exhaust duct 11 at 10L/min and if the air flow rate in the branch pipe 34 is assumed to be athe exhaust flow rate of the gas exhausted from the interior of theprocessing vessel 20 is (10−a) L/min. Since a is larger than 0, theexhaust flow rate of the gas exhausted from the interior of theprocessing vessel 20 is smaller than 10 L/min.

If the opening degree of the damper 35 decreases from the state shown inFIG. 3, the flow rate, a, of the air flowing from the branch pipe 34toward the exhaust pipe 30 becomes smaller. At this time, the flow rateof the air supplied from outside the processing vessel 20 into theprocessing vessel 20 through the gas inlet port 33 and then flowing intothe exhaust pipe 30 grows larger so as to compensate for the reductionin the amount of flow rate a. That is to say, the exhaust flow rate ofthe gas exhausted from the interior of the processing vessel 20increases. In this way, the damper 35 adjusts the flow rate ratio of theexhaust flow rate of the gas exhausted from the exhaust port 32 of theprocessing vessel 20 toward the exhaust duct 11 and the introductionflow rate of the gas introduced from the branch pipe 34 into the exhaustduct 11. Just like FIG. 3, FIG. 4 schematically shows a closed state ofthe damper 35. When the damper 35 is closed, the air flow rate a in thebranch pipe 34 becomes zero. For that reason, the exhaust flow rate ofthe gas exhausted from the interior of the processing vessel 20 is(10−0)=10 L/min. If the damper 35 is opened again from the state shownin FIG. 4, the value of the flow rate, a, increases. Thus, the exhaustflow rate of the gas exhausted from the interior of the processingvessel 20 becomes smaller again.

By opening and closing the damper 35 in this way, the exhaust flow rateof the gas exhausted from the interior of the processing vessel 20 isswitched. In the following description, the state in which the damper 35is opened as shown in FIG. 3 and the exhaust flow rate of the gasexhausted from the interior of the processing vessel 20 becomes smallerwill be sometimes referred to as low exhaust or a low exhaust state. Thestate in which the damper 35 is closed as shown in FIG. 4 and theexhaust flow rate of the gas exhausted from the interior of theprocessing vessel 20 becomes larger will be sometimes referred to ashigh exhaust or a high exhaust state. As set forth above, the heatingmodule 2A is configured such that air is supplied from the end portionof the branch pipe 34 and the gas inlet port 33 of the processing vessel20 into the exhaust duct 11, respectively. For that reason, even if thehigh exhaust and the low exhaust of the processing vessel 20 areswitched by opening or closing the damper 35 of the branch pipe 34, thevariation in the flow rate of the air flowing from the exhaust pipe 30toward the exhaust duct 11 is suppressed. Since the variation in theflow rate of the air flowing toward the exhaust duct 11 is suppressed inthis way, it is possible to suppress the variation in the exhaust flowrate of the air exhausted from the respective exhaust pipes 30 of theheating modules 2B and 2C toward the exhaust duct 11. This makes itpossible to suppress the variation in the exhaust flow rate of the airexhausted from the interior of the processing vessel 20 of each of theheating modules 2B and 2C. Similarly, even if the high exhaust and thelow exhaust are switched in each of the heating modules 2B and 2C, thevariation in the exhaust flow rate of the air exhausted from theinterior of the processing vessel 20 of another heating module issuppressed.

In view of the evaluation tests to be described later, in someembodiments, when the interior of the processing vessel 20 is in a lowexhaust state, the exhaust flow rate of the gas exhausted from theinterior of the processing vessel 20 is 0.16 μL/min or less. In order toset the exhaust flow rate at a sufficiently low value in this way, thebranch pipe 34 is configured such that the pressure loss in the branchpipe 34 is reduced and the flow rate of the air exhausted from thebranch pipe 34 is increased. A pressure loss in a pipe is inverselyproportional to the size of an inner diameter of the pipe and isproportional to the length of a flow path of the pipe. Therefore, thevalue (=A) obtained by dividing the length of a flow path of a pipe bythe inner diameter of a pipe in case of the branch pipe 34 is set tobecome sufficiently smaller than the value (=B) obtained by dividing thelength of a flow path of a pipe by the inner diameter of a pipe in caseof the exhaust pipe 30. For example, A/B becomes 1/25 or less.

Next, a description will be made on the controller 12 as a computershown in FIG. 1. A program stored in a computer-readable storage mediumsuch as, e.g., a flexible disk, a compact disk, a hard disk, a MO(magneto-optical) disk or a memory card, is installed in the controller12. Commands (individual steps) are incorporated in the installedprogram so that control signals can be transmitted to the respectiveparts of the heating device 1 to control the operations thereof.Specifically, individual operations such as the opening/closing of thedampers 35 in the respective heating modules 2A to 2C, the control ofelectric power supplied to the heater 22, the up/down movement of theshutter 26 and the lift pins 25, and so forth are controlled by theprogram.

In the heating modules 2A to 2C, the low exhaust state and the highexhaust state of the interior of the processing vessel 20 describedabove are switched during the process of heating the wafer W. Adescription will be made on the reason for performing the switching. Asdescribed in the BACKGROUND section, if the wafer W is heated, asublimate is generated from a coated film of a chemical solution formedon the surface of the wafer W. The sublimate becomes particles if it isattached to the wafer W or the inside of the processing vessel 20 and iscondensed. With a view to removing the sublimate from the interior ofthe processing vessel 20 and preventing contamination caused by theparticles, the exhaust in the high exhaust state is performed in someembodiments.

However, if processing is performed in the high exhaust state from thestart of processing of the wafer W to the end of processing of the waferW, the film thickness at the lower side of the exhaust port 32, namelyin the central portion of the wafer W, becomes larger than the filmthickness in the peripheral edge portion of the wafer W. The reason isas follows. Prior to generation of the cross-linking reaction, thecoated film has a low viscosity. The film thickness of the coated filmtends to be reduced when the coated film is exposed to an air flowwithin the processing vessel 20. In the high exhaust state, the airflowing from the peripheral edge portion of the wafer W toward thecentral portion thereof is sucked toward the exhaust port 32, namelyupward, prior to reaching the central portion of the wafer W. For thatreason, the film thickness in the central portion of the wafer W becomeslarger. That is to say, the film thickness in the central portion of thewafer W becomes larger because the central portion of the wafer W ishardly exposed to an air flow.

As the cross-linking reaction occurs, the viscosity of the coated filmgrows higher. If the coated film is cured, the film thickness of thecoated film is hardly affected by the air flow. Furthermore, if thetemperature of the wafer W becomes higher, a surpluslow-molecular-weight polymer or a surplus cross-linking agent issublimated. Thus, a sublimate is easily generated from the coated film.However, when the temperature of the wafer W remains low, a sublimate isnot generated. Accordingly, in some embodiments, a decrease in theuniformity of a film thickness distribution within a plane of the waferW is suppressed by maintaining a low exhaust state for a predeterminedtime from the start of processing of the wafer W, and then a sublimateis removed by maintaining a high exhaust state after the predeterminedtime is elapsed.

FIG. 5 is a graph showing the switching timing of the damper 35 when theexhaust is switched in the aforementioned manner during the heatingprocess of the wafer W. The vertical axis of the graph indicates thetemperature (degrees C.) of the wafer W. The horizontal axis of thegraph indicates the processing time. In the heating modules 2A to 2C,the processing is performed pursuant to this timing chart. As arepresentative example, the processing performed in the heating module24 will be described. For example, the damper 35 is first opened asshown in FIG. 3 before the water W having the coated film formed thereonis carried into the processing vessel 20. Thus, the interior of theprocessing vessel 20 is kept in a low exhaust state in which air isexhausted at an exhaust flow rate of 0.16 L/min or less. Then, the waferW is delivered to the lift pins 25 at the upper side of the heatingplate 21 heated to, e.g., 450 degrees C. The lift pins 25 are moved downsuch that the wafer W is mounted on the heating plate 21 (time T0).Since the interior of the processing vessel 20 is kept in the lowexhaust state, the air admitted from the outside of the processingvessel 20 into the processing vessel 20 flows from the peripheral edgeportion of the of the wafer W toward the central portion thereof, andthen flows toward the exhaust port 32 formed above the central portionof the wafer W. The air is exhausted through the exhaust port 32. Thatis to say, the temperature of the wafer W increases while the centralportion and the peripheral edge portion of the wafer W are all exposedto an air flow.

The temperature of the wafer W then reaches 250 degrees C. which is atemperature (cross-linking temperature) at which a cross-linkingreaction is started in the coated film. Thus, the coated film begins tocure. The temperature of the wafer W is further increased, whereby thecross-linking reaction and the curing of the coated film progress. Thisleads to an increase in the amount of a sublimate generated from thecoated film. At time T1 elapsed a predetermined time from time T0, thedamper 35 is closed as shown in FIG. 4 and the interior of theprocessing vessel 20 is switched to a high exhaust state. The intervalbetween time T0 and time T1 is, e.g., 10 seconds. In the high exhauststate, the sublimate generated from the coated film is rapidly exhaustedfrom the exhaust port 32 and is removed from the interior of theprocessing vessel 20. The temperature of the wafer W is furtherincreased to 450 degrees C. Thereafter, the wafer W is lifted up fromthe heating plate 21 by virtue of the lift pins 25. Thus, thetemperature of the wafer W is decreased and the damper 35 is opened(time T2) such that the interior of the processing vessel 20 is switchedto a low exhaust state. Then, the water W is carried out from theprocessing vessel 20 by a transfer mechanism.

Next, a description will be made on one example of the overall operationof the heating device 1. In the heating device 1, the water W isrepeatedly transferred, for example, in the order of the heating modules2A, 2B and 2C. A heating process is started in the heating module towhich the wafer W is transferred. During the heating process, theopening/closing of the damper 35 is switched as described with referenceto the graph shown in FIG. 5. The processed wafer W is carried out fromone of the heating modules 2A, 2B and 2C in which the heating process ofthe water W is completed. A subsequent wafer W is transferred to theheating module. Similar to FIG. 5, FIG. 6 is a graph showing theopening/closing switching timings of the dampers 35 of the respectiveheating modules 2A to 2C and the temperatures of the wafers W of therespective heating modules 2A to 2C when the aforementioned process isperformed. In the graph shown in FIG. 6, in order to distinguish theoperations of the respective heating modules from one another, the timeindicated by T1 in FIG. 5, at which the damper 35 is switched from anopen state to a closed state, is indicated by TA1, TB1, and TC1 withrespect to the heating modules 2A, 2B and 2C. The time indicated by T2in FIG. 5, at which the damper 35 is switched from a closed state to anopen state, is indicated by TA2, TB2 and TC2 with respect to the heatingmodules 2A, 2B and 2C.

Since the wafer W (a first wafer W) is transferred and processed in theorder of the heating modules 2A, 2B and 2C as described above, timeelapses in the order of the times TA1, TB1 and TC1. At the respectivetimes, the heating modules 2A, 2B and 2C are switched from the lowexhaust state to the high exhaust state. Similar to FIGS. 3 and 4, FIG.7 schematically shows the states of the dampers 35 of the respectiveheating modules 2A to 2C during a time period from the time TB1 to thetime TC1. In the heating modules 2A and 2B, the dampers 35 are closed tokeep the interior of the processing vessel 20 in the high exhaust state.In the heating module 2C, the damper 35 is opened to keep the interiorof the processing vessel 20 in the low exhaust state.

After the time TC1 elapses and the heating module 2C is switched to thehigh exhaust state, the heating processes of the first water W arecompleted in the order of the heating modules 2A, 2B and 2C. The firstwafer W is carried out from the processing vessel 20. Time elapses inthe order of the times TA2, TB2 and TC2. At the respective times, thedampers 35 of the heating modules 2A to 2C are opened and the heatingmodules 2A to 2C are switched from the high exhaust state to the lowexhaust state. Upon carrying out the first wafer W, a second wafer W iscarried into each of the heating modules 2A, 2B and 2C. The damper 35 isclosed during the processing of the second wafer W. That is to say, thesecond times TA1, TB1 and TC1 have elapsed. At the respective times, theheating modules 2A, 2B and 2C are switched from the low exhaust state tothe high exhaust state. In this example, the second time TA1 is set toexist, e.g., between the time TB2 and the time TC2.

Just like the first wafer W, the second wafer W transferred to each ofthe heating modules 2A to 2C is carried out from the processing vessel20 as soon as the processing thereof is completed. Upon completing theprocessing, the respective heating modules 2A to 2C are switched fromthe high exhaust state to the low exhaust state. That is to say, whilenot shown in FIG. 6, the second times TA2, TB2 and TC2 elapse in thenamed order. A subsequent wafer W is transferred and processed in theorder of the heating modules 2A, 2B and 2C. Upon completing a heatingprocess, the subsequent water W is carried out from the processingvessel 20.

In this way, the wafer W is individually transferred to the heatingmodules 2A to 2C and is individually subjected to the heating process inthe respective heating modules 2A to 2C. Thus, the opening/closingswitching of each of the dampers 35 is performed such that the switchingof the low exhaust state and the high exhaust state is individuallyperformed. When the opening/closing of the damper 35 is switched in oneof the heating modules 2A to 2C, the flow rate of the air flowing fromthe exhaust pipe 30 of the heating module into the exhaust duct 11 ismaintained at a constant rate as described with reference to FIGS. 3 and4. Therefore, the variation in the flow rate of the air flowing from theexhaust pipe 30 of another heating module into the exhaust duct 11 issuppressed. As a result, the variation in the exhaust flow rate of theair exhausted from the inside of the processing vessel 20 in anotherheating module is prevented.

According to the heating device 1 described above, each of the heatingmodules 2A, 2B and 2C sharing the exhaust duct 11 with one anotherincludes: the processing vessel 20 configured to heat the wafer W whilepurging the wafer processing atmosphere with the air introduced from thesurroundings; the exhaust pipe 30 configured to interconnect the exhaustduct 11 and the processing vessel 20; the branch pipe 34 branched fromthe exhaust pipe 30 with one end portion thereof opened to theatmosphere; and the damper 35 configured to open and close the flow pathof the branch pipe 34. In this configuration, the amount of air admittedfrom the branch pipe 34 into the exhaust duct 11 is controlled byopening or closing the damper 35. This makes it possible to control theexhaust flow rate in the processing vessel 20 and to suppress thevariation in the flow rate of the air flowing from the exhaust pipe 30toward the exhaust duct 11. Accordingly, even if the exhaust flow ratein the processing vessel 20 of one heating module is changed, there isno possibility that the exhaust flow rate in the processing vessel 20 ofanother heating module is changed resultantly. Therefore, when switchingthe interior of the processing vessel 20 to the low exhaust state andthe high exhaust state, it is possible to accurately control the exhaustflow rate in the respective exhaust states. Accordingly, it is possibleto reduce deterioration of a film thickness distribution within a planeof the wafer W. It is also possible to restrain a sublimate fromremaining within the processing vessel 20 and to restrain particlesgenerated from the sublimate from adhering to the wafer W or theprocessing vessel 20. In addition, the branch pipe 34 provided with thedamper 35 does not need to be kept at a high temperature in order toprevent condensation of the sublimate. It is therefore possible toprevent the damper 35 from being damaged by heat.

In the processing example described above, the wafer W is mounted on theheating plate 21. After a predetermined time, the damper 35 is closed toswitch the low exhaust state to the high exhaust state. Instead oftime-dependently controlling the damper 35 in the aforementioned manner,for example, a radiation thermometer may be installed in the processingvessel 20 so that the temperature of the wafer W can be measured by theradiation thermometer. The damper 35 may be controlled such that, if thetemperature of the wafer W thus measured reaches a predeterminedtemperature, the damper 35 is closed.

In the processing example described above, the low exhaust state and thehigh exhaust state are instantly switched to each other. However, theswitching may be gradually performed. Similar to FIG. 5, FIG. 8 is agraph showing the relationship between the opening/closing timing of thedamper 35 and the temperature of the wafer W. FIG. 8 shows an example inwhich the damper 35 is controlled such that the switching from the lowexhaust state to the high exhaust state is gradually performed. Adescription will be made primarily on a difference between theprocessing shown by the graph of FIG. 8 and the processing describedwith the graph of FIG. 5. The processing vessel 20 is kept in the lowexhaust state. At time T0, the wafer W is mounted on the heating plate21. Thereafter, the opening degree of the damper 35 begins to be changedat, e.g., time T11 at which the temperature of the wafer W becomes equalto 250 degrees C., i.e., the cross-linking temperature. The openingdegree of the damper 35 is gradually reduced. The amount of airintroduced from the branch pipe 34 into the exhaust pipe 30 is graduallydecreased while the exhaust flow rate in the processing vessel 20 isgradually increased. At time T12, the damper 35 is closed. Thus, theflow rate of the air in the protrusion portions 43 becomes zero and theprocessing vessel 20 is switched to the high exhaust state. The intervalbetween time T11 and T12 is 5 seconds or more. In this example, theinterval between time T11 and time T12 is 10 seconds. The intervalbetween time T0 and time T11 is, e.g., 5 seconds.

The reason for gradually closing the damper 35 is as follows. If thedamper 35 is suddenly closed, the air does not suddenly flow from theair atmosphere toward the downstream side of the damper 35 of the branchpipe 34. Thus, the pressure is reduced at the downstream side of thedamper 35. Due to this pressure reduction, it is likely that thesublimate flowing from the processing vessel 20 into the exhaust pipe 30does not move toward the exhaust duct 11 but flows into the branch pipe34 where the sublimate is condensed. That is to say, by graduallyclosing the damper 35, it is possible to prevent condensation of thesublimate in the branch pipe 34 and to prevent particles otherwisegenerated from the sublimate from scattering toward the processingvessel 20 when the air flows through the branch pipe 34 with the damper35 opened again.

FIG. 9 shows a modification of the heating module 2A. On the lowersurface of the cover 31 of the heating module 2A shown in FIG. 9, gasinlet ports 41 are formed so as to be opened toward the outer side ofthe wafer W mounted on the heating plate 21. For example, the pluralityof gas inlet ports 41 are formed along the circumference of the wafer Wand are connected through a pipe line 42 to a supply source 43 of air asa purge gas. A heating part 44 is installed in the pipe line 42 to heatthe air flowing through the pipe line 42. The temperature of the airsupplied from the gas inlet ports 41 is maintained by the heating part44 at a temperature of, e.g., 40 degrees C. or higher.

If the heating module 2A performs processing in the same manner asshower the graph of FIG. 5, the damper 35 is closed at, e.g., time T1,and the interior of the processing vessel 20 is kept at the high exhauststate. The air heated by the heating part 44 begins to be supplied tothe respective gas inlet ports 41. By the supply of the air, the exhaustflow rate of the air exhausted from the exhaust port 32 can be reliablykept high. It is therefore possible to efficiently and reliably removethe sublimate. Thereafter, the damper 35 is opened at, e.g., time T2,and the interior of the processing vessel 20 is kept at the low exhauststate. The supply of the air is stopped.

Since the air heated by the heating part 44 is supplied from the gasinlet ports 41, it is possible to prevent the sublimate from beingcooled and condensed by the air. During the processing of the wafer W,the temperature of the processing vessel 20 is increased by the heatingplate 21. Therefore, an air flow path may be formed in the cover 31 suchthat the air supplied from the supply sources 43 to the cover 31 isheated by the heat of the heating plate 21 before the air is ejectedfrom the gas inlet ports 41 toward the processing atmosphere. In thiscase, it may be possible to employ a configuration in which the heatingpart 44 is not installed. The gas inlet ports 41 are not limited tobeing formed in the cover 31. As an example, the gas inlet ports 41 maybe installed outside the wafer mounting region of the heating plate 21.Moreover, the external gas supplied into the processing vessel 20 is notlimited to air. An inert gas such as a nitrogen gas or the like may besupplied into the processing vessel 20. The external gas supplied intothe processing vessel 20 includes a gas introduced from the gas inletport 33 and a gas supplied from the supply source 43.

FIGS. 10 and 11 show another configuration example of the damper 35. Inthis example, the damper 35 is installed in a connection portion of theexhaust pipe 30 to which the branch pipe 34 is connected. In theconnection portion, a state in which the air can flow from thedownstream end of the branch pipe 34 into the exhaust pipe 30 and astate in which the flow of the air is cut off are switched to each otherby the damper 35. Thus, the interior of the processing vessel 20 isswitched to a low exhaust state or a high exhaust state. That is to say,the damper 35 may not be installed in the branch pipe 34 but may beinstalled in the exhaust pipe 30 as mentioned above.

The heating device 1 can be used in heating, e.g., a wafer W coated witha chemical solution for forming an anti-reflection film below a resistfilm. The chemical solution for forming the anti-reflection filmcontains a low-molecular-weight polymer and a cross-linking agent. At atemperature lower than a cross-linking temperature, the film thicknessis easily affected by air flow. For that reason, in some embodiments, aheating process is performed by switching a low exhaust state and a highexhaust state as described above. The heating device 1 is not used onlyin processing the wafer W coated with the chemical solution capable ofgenerating the cross-linking reaction. As an example, the heating device1 may be used to heat a wafer W coated with a resist solution which doesnot generate the cross-linking reaction. If the temperature of theresist solution is low and if the viscosity of the resist solution islow due to the inclusion of a large amount of solvent, the filmthickness of a resist film is easily affected by an air flow. For thatreason, just like the processing of the organic film or theanti-reflection film described above, in some embodiments, the heatingprocess is performed in a low exhaust state up to the temperature atwhich the generation amount of a sublimate becomes relatively largealong with the curing of the film, and then the heating process isperformed in a high exhaust state. In the processing performed by therespective heating modules 2A to 2C, it is only necessary that, in thelow exhaust state, the uniformity of the film thickness distribution ofthe wafer W is not deteriorated. Therefore, the exhaust flow rate in theprocessing vessel 20 may be 0 L/min. That is to say, no exhaust may beperformed in the low exhaust state.

(Evaluation Test)

Next, a description will be made on evaluation tests conducted withrespect of the present disclosure. In the evaluation tests, a wafer W of300 mm in diameter coated with a chemical solution for forming theaforementioned organic film was heated using the heating moduledescribed in the embodiment above. The heating was performed by changingthe exhaust flow rate in the processing vessel 20 on a wafer-by-waferbasis. In evaluation tests 1-1 to 1-5, unlike the processing in theaforementioned embodiment, the heating was performed by keeping theexhaust flow rate constant in the processing vessel 20 from the start ofthe processing of the wafer W to the end of the processing. Inevaluation tests 1-1, 1-2, 1-3, 1-4 and 1-5, the exhaust flow rates wereset at 15 L/min, 0 L/min, 0.3 L/min, 0.5 L/min and 1 L/min,respectively. In evaluation test 1-6, as described in the embodiment,the switching from a low exhaust state to a high exhaust state wasperformed during the processing of the wafer W.

With respect to the wafers W processed in evaluation tests 1-1 to 1-6,the film thicknesses at a plurality of points within a plane weremeasured to calculate an average value, a 3-sigma, a range, a centerrange and an improvement rate. The term “range” refers to a differencebetween the maximum value and the minimum value of the film thicknessesacquired from the wafer W. The term “center range” refers to adifference between the film thickness measured at the center of thewafer W and the film thickness measured at one point spaced apart apredetermined distance from the center of the wafer W. The term“improvement rate” refers to an improvement rate of the center rangeacquired in other evaluation tests when the center range of evaluationtest 1-1 is used as reference value. The improvement rate is representedby (the center range of evaluation test 1-1−the center range acquired inother evaluation tests)/(the center range of evaluation test 1-1)×100(unit: %).

Table 1 shown below indicates the measurement results of evaluationtests 1-1 to 1-6. Furthermore, the graph shown in FIG. 12 indicates thecenter range and the improvement rate obtained in evaluation tests 1-1to 1-5. The horizontal axis of the graph indicates the exhaust flow ratein the processing vessel 20. The vertical axis of the graph indicatesthe center range and the improvement rate. The measurement results areplotted in the graph. In addition, approximate curves obtained based onthe measurement results are shown in the graph. As shown in Table 1, theaverage film thicknesses obtained in evaluation tests 1-1 to 1-6 aresubstantially equal to one another. Evaluation test 1-6 is lower in the3-sigma, the range and the center range, than evaluation tests 1-1 to1-5 but is higher in the improvement rate than evaluation tests 1-1 to1-5. Accordingly, it was confirmed that, if the processing is performedby switching the low exhaust state and the high exhaust state asmentioned in the above-described embodiment, the uniformity of thein-plane distribution of the film thickness of the water W can be madehigher. Furthermore, in some embodiments, the improvement rate is set at50% or less. It can be noted from the approximate curves of the graphshown in FIG. 12 that the exhaust flow rate is 0.16 L/min when theimprovement rate is 50% and further that the improvement rate growshigher as the exhaust flow rate becomes lower. Accordingly, when theinterior of the processing vessel 20 is kept in the low exhaust state inthe above-described embodiment, the exhaust flow rate is set at 0.16L/min or less.

TABLE 1 Evaluation test 1-1 1-2 1-3 1-4 1-5 1-6 Exhaust flow rate(L/min) 15 0 0.3 0.5 1 low → high Film thickness average value (nm)245.4 245.7 245.6 245.7 246.0 245.0 3-sigma 5.6 3.6 3.3 3.5 3.7 2.3Range (nm) 10.58 4.50 4.36 4.90 5.73 3.36 Center range (nm) 8.06 3.134.54 5.60 6.06 2.72 Improvement rate (%) — 61 44 31 25 66

According to the present disclosure, the substrate heating deviceincludes a common exhaust path connected to individual exhaust paths ofa plurality of heating modules, a branch path branched from each of theindividual exhaust paths and opened to the outside of a processingvessel, and an exhaust flow rate adjusting part configured to adjust aflow rate ratio of an exhaust flow rate of a gas exhausted from anexhaust port for the exhaust of the interior of the processing vesselinto the common exhaust path and an introduction flow rate of a gasintroduced from the outside of the processing vessel into the commonexhaust path through the branch path. This makes it possible to changethe exhaust flow rate of the gas exhausted from each of the individualexhaust paths of the heating modules and to suppress variation in theexhaust flow rate of the gas exhausted from the individual exhaust pathsto the common exhaust path, which may be caused by the change of theexhaust flow rate. Accordingly, it is possible to accurately control theexhaust flow rate in the processing vessel of each of the heatingmodules. As a result, it is possible to reduce deterioration of thein-plane uniformity of a coated film formed on a substrate through aheating process. It is also possible to prevent the interior of theprocessing vessel from being contaminated by a sublimate generated fromthe coated film.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A substrate heating method which makes use of asubstrate heating device including: a plurality of heating modules, eachof which includes a processing vessel within which a heating plate formounting and heating a substrate is disposed, an gas inlet port forintroducing a purge gas into a processing atmosphere existing within theprocessing vessel, and an exhaust port for exhausting the processingatmosphere; individual exhaust paths, each of which is connected to theexhaust port of each of the plurality of heating modules; and a commonexhaust path connected to downstream ends of the individual exhaustpaths of the plurality of heating modules; and a branch path branchedfrom each of the individual exhaust paths and opened to the outside ofthe processing vessel, the method comprising: mounting the substrate onthe heating plate; adjusting, with an exhaust flow rate adjusting unit,a flow rate ratio of an exhaust flow rate of a gas exhausted from theexhaust port into the common exhaust path and an introduction flow rateof a gas introduced from the outside of the processing vessel into thecommon exhaust path through the branch path, thereby maintaining a lowexhaust state in which the processing atmosphere is exhausted at a lowexhaust flow rate; and subsequently, adjusting the flow rate ratio withthe exhaust flow rate adjusting unit, thereby maintaining a high exhauststate in which the processing atmosphere is exhausted at a flow ratehigher than the low exhaust flow rate.
 2. The method of claim 1,wherein, after the substrate is mounted on the heating plate, theprocess of maintaining the low exhaust state is performed until a timeincluding a time period during which, if the high exhaust state isselected, the in-pane uniformity of a film thickness deteriorates due toa low viscosity of a coating solution coated on the substrate, and afterthe time period elapses, the process of maintaining the high exhauststate is performed to remove a sublimate generated from a coated film.3. The method of claim 1, wherein the low exhaust state is switched tothe high exhaust state by gradually changing the flow rate ratio withthe exhaust flow rate adjusting unit.
 4. The method of claim 1, whereinthe purge gas is heated by a heating unit and is then introduced intothe processing atmosphere through the gas inlet port.
 5. Anon-transitory computer-readable storage medium which stores a computerprogram used in a substrate heating device for heating a substratemounted on a heating plate, wherein the program incorporates steps forimplementing the substrate heating method of claim 1.